The United States launched war on Iraq early Thursday with air strikes on Baghdad, making good on threats of military action to push President Saddam Hussein out of power.

US President George W. Bush announced that war had begun and that coalition forces had "begun striking selected targets of military importance," as explosions were heard shattering the dawn sky in Baghdad.

Clouds of smoke billowed at the edges of the Iraqi capital, where Washington says Saddam has been leading a regime dedicated to developing weapons of mass destruction and must now be thrown out.

An AFP correspondent in Baghdad said anti-aircraft batteries were heard firing in the Iraqi capital during two air strikes within an hour of each other, marking the beginning of a military conflict that has torn apart the world community.

The sound of jet engines was also heard, but it was not immediately known if they were warplanes or cruise missiles.

"My fellow citizens, at this hour, American and coalition forces are in the early stages of military operations to disarm Iraq, to free its people and to defend the world from grave danger," Bush said in a televised address.

The US military had refused all comment on the movement of its forces after 0100 GMT, the deadline laid down by Bush for Saddam and his sons to quit the country or face the world's mightiest military.

More than 250,000 US and British ground troops, backed up by a massive naval armada as well as hundreds of warplanes at the ready in the Gulf, are massed on the outskirts of Iraq but there was no immediate word on their movements.

Bush and his closest ally on Iraq, British Prime Minister Tony Blair, say Saddam is harbouring weapons of mass destruction and have vowed to see him ousted from the country he has ruled with an iron grip since 1979.

But Saddam and the Iraqi leadership insist that US troops will meet their death in the desert sands of Iraq, which is facing its second US-led war since 1991, when US forces led a coalition to eject Saddam's troops from Kuwait.

In a televised address Monday that was watched around the world, Bush said the time had come to push Saddam out of power, and gave him 48 hours to flee or face an invasion from the world's mightiest army.

But the Iraqi leader rejected the ultimatum as "despicable" and repeatedly vowed that he would choose to die in his homeland rather than surrender under US pressure.

The prospect of a US-led war has shattered the world community and strained relations between Washington and longtime allies such as France, while drawing warnings from Islamic militants of attacks on US interests worldwide.

UN Secretary General Kofi Annan even took the unusual step of critisising the United States, amid what has been widely seen as a US diplomatic failure to rally international support for an attack to topple Saddam.

Bush has linked Iraq to an "axis of evil" that includes next-door Iran as well as North Korea, and says Saddam is a tyrant who must be ousted as part of Washington's campaign against terrorism.

But Saddam has vowed to resist and the Iraqi parliament on Wednesday gave him unanimous support, with MPs pledging to die to defend him.

Saddam on Wednesday said Iraq no longer had weapons of mass destruction, which Washington originally insisted was the source of its concern over Baghdad after the September 11 attacks.

UN arms inspectors, tasked under UN Security Council resolutions to verify that Baghdad harbours no chemical, biological or nuclear weapons, were pulled out of the country in the hours before Bush's deadline.

But Washington has since said that eliminating such weapons is not enough, and that Saddam and the Iraqi leadership must go. Sapa-AFP